Lbz Knocking

Shawn T · October 19, 2009

Recently, I am getting a really loud knock out of my LBZ. Only 41000 miles and it only does it when it's cold. It sounds like a sticky valve, but about 3 times louder. As soon as it warms up, it goes away. Not normal. Started about 3000 miles ago. Only prob, I've seen with the LBZ motor is a sticky EGR valve. I can pretty much rule this out, as it does not blow an ounce of smoke. Help is appreciated.

masterp2 · October 19, 2009

Do you have a tuner on it?

Sounds like tuner knock, these tuners are so badly written, they rattle hard in cold weather.

Justind1203 · October 19, 2009

Do you have a tuner on it?

Sounds like tuner knock, these tuners are so badly written, they rattle hard in cold weather.

Yeah it will fuel rattle when its cold.

Shawn T · October 19, 2009

Do you have a tuner on it?

Sounds like tuner knock, these tuners are so badly written, they rattle hard in cold weather.

Yeah it will fuel rattle when its cold.

No tuner, bone stock except for a Dynomax free flow muffler. I also ditched the cat.

Kodiak450 · October 19, 2009

GM makes one of the best knock control sensors. What grade fuel are you using? Might want to try using a grade up for a few tanks and see if the knocking goes away eventially.

Shawn T · October 19, 2009

GM makes one of the best knock control sensors. What grade fuel are you using? Might want to try using a grade up for a few tanks and see if the knocking goes away eventially.

Last I checked diesel has one grade. ultra low sulfer fuel oil. It's fuel rattle in a diesel. I guess I should have explained it better. I thought the LBZ part gave it away. I'm not diesel expert, this is why I need some experienced advice.

Kodiak450 · October 19, 2009

GM makes one of the best knock control sensors. What grade fuel are you using? Might want to try using a grade up for a few tanks and see if the knocking goes away eventially.

Last I checked diesel has one grade. ultra low sulfer fuel oil. It's fuel rattle in a diesel. I guess I should have explained it better. I thought the LBZ part gave it away. I'm not diesel expert, this is why I need some experienced advice.

Opps, sorry. Thought we were talking gas engines here.

Justind1203 · October 19, 2009

Do you have a tuner on it?

Sounds like tuner knock, these tuners are so badly written, they rattle hard in cold weather.

Yeah it will fuel rattle when its cold.

No tuner, bone stock except for a Dynomax free flow muffler. I also ditched the cat.

I would have it checked out, its under warranty right? Can't hurt to have it looked at.

Shaners · October 19, 2009

Maybe it is an injector going bad. Do you run adative from time to time? I don't use it in mine except in the winter to help gelling, but othe people I know use it religiously since the switch to ULSD. They claim that sulfer was to diesel as lead was to gasoline. It is a type of lubricant... try some adative in the next few tanks and see if it helps any.

Kodiak450 · October 19, 2009

You could alos try filling up at a different station with a different brand if it's possible in your area. I remember years back when we had a few diesels and they would perform poorly when they were refueled at a certain station.

Shawn T · October 20, 2009

Maybe it is an injector going bad. Do you run adative from time to time? I don't use it in mine except in the winter to help gelling, but othe people I know use it religiously since the switch to ULSD. They claim that sulfer was to diesel as lead was to gasoline. It is a type of lubricant... try some adative in the next few tanks and see if it helps any.

Shaners, that was my next venture. What do you recommend? It has 41K on it, the duramax is still covered, but I'm sure I will have to pay a deductable now that the 36K mile warranty has expired. Could a bad injector just plug up under cold situations, then unclogg after it warms up? Should I duplicate this post under "GM Tech" to see if a diesel mechanic may know it off of the bat?

Shaners · October 20, 2009

I buy my additive at the truck stop and run what they run in the big rigs. I figure those guys know more than the kid at AutoZone...

Justind1203 · October 20, 2009

I believe 5yr 100k mile powertrain warranty on Duramax powered trucks.

98silvz71 · October 20, 2009

You could alos try filling up at a different station with a different brand if it's possible in your area. I remember years back when we had a few diesels and they would perform poorly when they were refueled at a certain station.

This is what I had to do. Some stations will add 5% biodiesel without telling you, Murphy Oil at Wal-Mart does in my town. So I just run Shell diesel. I have the best luck with it.

Maybe it is an injector going bad. Do you run adative from time to time? I don't use it in mine except in the winter to help gelling, but othe people I know use it religiously since the switch to ULSD. They claim that sulfer was to diesel as lead was to gasoline. It is a type of lubricant... try some adative in the next few tanks and see if it helps any.

Shaners, that was my next venture. What do you recommend? It has 41K on it, the duramax is still covered, but I'm sure I will have to pay a deductable now that the 36K mile warranty has expired. Could a bad injector just plug up under cold situations, then unclogg after it warms up? Should I duplicate this post under "GM Tech" to see if a diesel mechanic may know it off of the bat?

It wouldn't hurt to have it looked at. As long as its under warranty. Just make sure you tell them to let you know what they find out before they fix anything. That way you won't have to pay any deductible.

I buy my additive at the truck stop and run what they run in the big rigs. I figure those guys know more than the kid at AutoZone...

I will run Power Service power cleaner in the gray bottle during the summer to clean out the injectors. It really works on my LB7 with the touchy injectors. And during the winter I run Howe's Lubricator for the diesel treat. Howe's is a good all around additive.

I believe 5yr 100k mile powertrain warranty on Duramax powered trucks.

Yes, but after 36K there is a deductible to pay or at least there was on trucks before the 100,000 mile warranty for all vehicles. I think it is less than $500 but still an expense he would have to pay to get service done.